Electrically operated soap and/or foam dispensers for hand washing are generally activated in a contactless manner by a sensor, i.e. a hand held out at a suitable distance sets a pump mechanism in action, so a portion of soap or foam is dispensed. If the hand is withdrawn prematurely or if someone wishes to xe2x80x9ctestxe2x80x9d the action of the dispenser by passing the hand underneath quickly, the dispensed portion falls on parts of the wash basin and/or soils the floor.
This drawback has been recognised and an attempt made to eliminate it by reversing the direction of rotation of the drive motor as set forth in DE-A1-198 05 304. Here the presence of the hand to be provided with soap is monitored during the is pumping process. The necessary change in the drive and the subsequent mechanism from a forward direction to a reverse direction represents a complete reversal in the flow of energy and causes motor currents which are a multiple of the nominal current. Repeated successive actuation of the change in the direction of rotation can overheat and damage a small motor. In addition, the control circuit has to be equipped with components (transistors/thyristors, passive elements) which can process the maximum resulting high currents and are correspondingly expensive.
The object of the present invention is therefore to create a device which manages dispensation without the reversal of a drive motor, is economical and yet satisfies the requirements in service. The subject of the invention should stop the drive when the hand to be provided with soap is not removed at the correct time such that there is no soiling of the dispenser and its surroundings. In addition, the dispenser should be ready for use again after a short time and must not incur any damage even after repeated incorrect triggering of the metering process.
This object is achieved by the use of switchable coupling members between the drive motor and a piston rod of the pump member. A sensor controls the operation of the coupling members, which disengage the pump from the motor when a hand is not in the proper position for receipt of the pumped media.
Owing to the uncoupling of the piston rod the flow of power to the pumping member is interrupted so the flow of medium is stopped immediately. The relief applied to the pumping member and corresponding elastic components is sufficient in most devices to cause minimum backlash, preventing dripping of the medium.
The switchable members may be located between a push rod and the piston rod. The push rod converts the rotational movement of the motor into an oscillating movement in a compact manner. Transmission of the movement of the push rod to a coupling link facilitates the interruption and the subsequent restoration of the flow of power.
Inclusion of a locking cam and a spring-loaded locking lever on the push rod is particularly advantageous for quick unlocking and locking, i.e. for connection to the coupling link with an interlocking fit. Electromagnetic disengagement of the locking lever can also be provided.
A connecting link can be utilized to actuate the locking lever. Rotational loading of the connecting link through a joint head construction allows virtually any arrangement of the electromagnet and requires only small forces for uncoupling. Such a construction also allows the use of commercially available actuating magnets.
The joint head also allows an oscillating movement of the push rod to be converted into a linear pumping movement.
A leaf spring can be used to act on the connecting link and ensures reliable disengagement thereof.
An additional restoring force f applied to the piston increases the inherent backlash in the pumping member and prevents subsequent dripping, in particular if soap flakes undergo an expansion at an inner face next to the delivery aperture. The force should be as small as possible to conserve energy.